My question: if my opponent makes a dangerous play that endangers his teammate but does not endanger any of my teammates, can I still call a dangerous play foul against him?
The reason I'm finding the rules ambiguous is that 17.1.1 defines dangerous play using the phrase "fellow players" instead of "opposing players":
Actions demonstrating reckless disregard for the safety of fellow players, or posing significant risk of injury to fellow players,...
This use of "player" instead of "opponent" is also present in the annotation for 17.1.1:
The following are non-exhaustive examples of dangerous play:
• significantly colliding with a mostly stationary opponent,
• jumping into a group of mostly stationary players,
• diving around or through a player that results in contact with a player's back or legs,
But, on the other hand, 15.1 is pretty clear in limiting a foul to contact between opposing players:
A breach of the rules due to non-minor contact between two or more opposing players is a foul.
15.1 suggests that jumping into a group of stationary teammates is not a dangerous play foul, at direct odds with the 17.1.1 annotation.
If a player from Team A jumps into another player from Team A, Team B can not call Dangerous Play.
Team B could discuss the play with Team A, especially if it was a reckless play that could just as easily resulted in a collision with a player from Team B.
If Team B think that Team A used the collision with their teammate to assist them to contact the disc, they could call a violation as per rule 12.10